I was thinking today (Yeah, dangerous, I know).
If we think back to the release of the HP-41C and how this was reported in PPC, it seems possible to me that HP lent a hand in the "discovery" if not the creation of synthetic programming.
Some time ago I thought I would re-read PPC articles just to see how HP-41C synthetic programming was discovered and developed. Imagine my surprise to find that quite detailed knowlege of it was evident right from the first review of the calculator.
As I think back to that time, it was a point when TI and HP were going hammer and tong (as were their users) to prove that they had the better calculator.
Calculator owners back then were pretty technically minded, a bit like the first computer owners, the first internet users, etc. What better way to attract them than provide a host of interesting and dangerous features? What better way to make them the subject of cult following by officially denying, if not their existance, certainly any support.
But did they REALLY deny support? It would have been quite easy for HP in one of their ROM revisions to make many of these synthetic functions (such as RCL c, or STO M) result in a NONEXISTANT error, but they didn't.
Some calculator bugs were fixed quite soon. But these were ones that could cause strange (and perhaps destrucive) behaviour in normally written code. These included the STO IND, and SF/CF IND bugs, and the non-decompiling when switching out of program mode. But those bugs that gave access to synthetic programming (Deleting program lines in CAT mode and strange key assignments were never touched.
So, I wonder.... Who was it who made the policy decision? Who in HP either briefed users as to what these instructions were, or who provided information in such a way as to allow its easy "discovery"?
Hmmmmmmmmmmmmm.....